alphagov/transition — pull request #455 by fatbusinessman (2014-11-11 14:02:58+00:00)
Title: Flip the uniqueness constraint on Mapping

While the effect is the same either way (that no two `Mapping` objects can have the same values for both `path` and `site_id`), it's clearer this way around that the idea is to ensure no two mappings exist for the same path in a site.